1. Field of the Invention
The present invention relates to a snow-melting light-emitting diode (LED) traffic signal, which can inhibit snow accretion, ice accretion, frost accretion, freeze of snow, freeze of ice, freeze of frost, and the like promptly without fail, and can obtain satisfactory visibility.
2. Description of the Related Art
A traffic signal is a device which is indispensable for ensuring safety of road traffic and smoothness of a traffic flow.
In recent years, installation of, as such traffic signals, LED traffic signals has already been carried out in the respective prefectures here in Japan as a national policy making use of characteristics of LEDs such as low power consumption and long life. At present, ⅓ to ¼ of incandescent signals installed in Japan have been replaced by LED signals.
In Japan, which being long in a north-south direction, except for southern parts thereof and the like, snow, ice, or frost accretes to traffic signals in winter or the like to lower the visibility of the traffic signals, which is an obstacle to safe road traffic.
Still, in a conventional incandescent (60 W) traffic signal, the incandescent lamp itself generates heat, and thus, the problem of snow accretion, ice accretion, and the like has not been so serious compared to the present situation owing to the generated heat.
However, an LED traffic signal is more excellent in energy efficiency with lower power consumption, but generates less heat compared to those of a conventional traffic signal, which adversely affect the situation to thereby arise a problem frequently such that snow or ice accretes to traffic signals in winter or the like and a signal light is hardly visible, whereby leading to a serious accident.
Therefore, measures to prevent snow accretion, ice accretion, frost accretion, freeze of snow, freeze of ice, and freeze of frost are strongly desired especially with regard to LED traffic signals installed in snowy areas and high-altitude areas.
Further, both an incandescent traffic signal and an LED traffic signal generally have an eave attached thereto. When snow accumulates, a problem arises that a snow buildup on or an icicle hanging down from the eave weights the signal no matter whether the signal is of a vertical type or of a horizontal type, which places a heavy load on a signal pole to be a cause of a failure.
Therefore, both for the purpose of ensuring the visibility of traffic signals and for the purpose of maintaining bodies of the signals, man power has been used to remove snow, icicles, and the like attached to traffic signals installed in snowy areas and high-altitude areas, but this work requires enormous efforts under severe circumstances.
Therefore, for example, a snow buildup removing hood device is proposed in which a protruding portion is attached above an eave of a traffic signal, and a circular tubular hood including a ring-like frame portion having a plumb attached thereto is fit onto the eave to separate and slide down a snow buildup to be removed (Japanese Utility Model Registration No. 3072584). However, such a device is heavy and large to some extent.
Therefore, the inventors of the present invention diligently made a study of development of an LED signal which was able to inhibit more effectively snow accretion, ice accretion, frost accretion, freeze of snow, freeze of ice, freeze of frost, and the like and which was able to obtain satisfactory visibility. The result was that the inventors of the present invention developed an LED traffic signal in which a heat generating plate is placed in proximity to an air vent in a printed board protection cover (Japanese Utility Model Registration No. 3163928).
This LED traffic signal exhibited the effect of inhibiting snow accretion, ice accretion, frost accretion, freeze of snow, freeze of ice, freeze of frost, and the like to some extent, but the snow melting speed was not so high and far infrared radiation was not emitted substantially uniformly over substantially the entire surface of the LED signal light. Thus, the LED traffic signal was not necessarily satisfactory.